Information entropy of mixing molecules and its application to molecular ensembles and chemical reactions

Abstract

We have deduced a general formula for information entropy of mixing, which is the change in information entropy when two or more molecules form an ensemble. The sign of this quantity depends on the sort and internal structure of the mixing molecules and may be zero even when they differ. This implies a striking difference from thermodynamic entropy, which cannot be nonzero when mixing different particles. The information entropy of a molecular ensemble has been expressed through the information entropies of the constituting molecules and exemplified with real chemical systems. Information entropy of a molecular ensemble depends on the fractions of the members, their information entropies and includes cooperative information entropy, the additional term attributed to the phenomenon of mixing. Application of this approach to chemical reactions allows considering a chemical reaction as the combination of changes in molecular structure and molecular size and almost separate assessing these contributions.